Brazil's first team have not trained as a unit since Tuesday's draw with Mexico, prompting concerns over the lack of urgency in a side that were disappointing in their opening two World Cup games.

Manager Luiz Felipe Scolari has long known his starting 11 and that team beat Croatia 3-1 in the tournament opener. He made one change to the side that drew 0-0- with Mexico, bringing in Ramires for Hulk, who had been suffering with a thigh injury.

Scolari led a technical training session on Friday, at which players practiced drills as separate defensive and attacking units.

The squad had a day off after the scoreless draw in Fortaleza and the first team were spared training on Thursday because of heavy rain.

With only two more opportunities to drill the first 11 before they face Cameroon in Brasilia on Monday, some observers have questioned Scolari's methods.

"They've got the training wrong," Dada Maravilha, a former player and now TV commentator told Reuters at Brazil's base camp outside Rio de Janeiro.

"This is the World Cup, you should be training the team, working them together. Brazil need to perform much better than they've performed up to now."

The host nation are seeking to secure first place in Group A against Cameroon to secure a last 16 encounter with the loser of the Group B match between the Netherlands and Chile. Brazil top the group with four points, ahead of Mexico on goal difference.

COMPETITIVE LEVEL

Brazil's 0-0 draw with Mexico ended a 10-game winning streak and the players admit they still have not hit anything like top gear.

"We have to improve a few things, of course, but we do that (by) playing," said left back Marcelo. "Now we have a game against Cameroon to improve things."

Center half David Luiz said the players were still adjusting to a more competitive level after the Confederations Cup and a year of friendlies. As host nation, Brazil qualified automatically for the 2014 World Cup.

"We know that we can get better, that we can grow, but we also know what we're up against," Luiz told reporters at Brazil's training camp outside Rio de Janeiro.

"When you compare the Confederations Cup with the World Cup it's not the same, all the teams are very prepared for the World Cup. The level today is very high."

Marcelo said Brazil's fine performance at the Confederations Cup, when they won all five games and handed world and European champions Spain their heaviest competitive defeat in almost 40 years, had enabled their opponents to prepare for them.

"Many teams have studied us so it's harder now," he said. "We know we have to do what Felipao (coach Luiz Felipe Scolari) tells us but that's the World Cup, each game is harder than the one before."

Cameroon are bottom of the group having lost both their games to Mexico and Croatia.